The present invention relates generally to foamed tobacco products, and more particularly to an efficient method of producing foamed tobacco products with uniform characteristics.
It is known from U.S. Pat. No. 3,872,871 to make low density cigar tobacco sheet material from a foamed intermediate having a particular bubble size distribution, resulting in a product that is said to have excellent taste. In order to obtain a high quality foam, a stabilizer is added to the slurry prior to high speed agitation. Known stabilizers, such as ethylhydroxyethylcelluloses, are mixed ethers of cellulose prepared by the reaction of alkali cellulose with ethylene oxide, to make hydroxyethoxyl groups, and with ethyl chloride, to make ethoxyl groups. The hydroxyethoxyl groups render the resulting polymer more hydrophilic, while the ethoxyl groups render it more hydrophobic. U.S. Pat. No. 3,872,871 describes an ethylhydroxyethylcellulose (EHEC) derivative which is relatively more highly substituted with ethoxyl groups, as is evidenced by its having a cloud point (the temperature at which the polymer starts to come out of solution, when heated) of only 30-40° C. (86-104° F.).
U.S. Pat. No. 3,613,693 describes a method for producing reconstituted tobacco products using a particular type of ethylhydroxyethylcellulose. The method requires the use of cool temperatures for foaming. More particularly, U.S. Pat. No. 3,613,693 states that the temperature should be 25° C. (77° F.) or less in order for the EHEC to dissolve in water. The patent further indicates that if the temperature of insolubility is reached during mixing of the slurry, foaming, transfer or shaping of the foam, precipitation of the EHEC will occur and the foam stabilization property of the EHEC will be lost. While the method described in this patent produces a useful product, it requires the use of a cooling stage prior to and/or during agitation in order to ensure that the EHEC stays soluble in the aqueous solution. The use of a cooling stage adds to the overall cost of the process.